Our laboratory develops and applies methods for assessing the function of central and peripheral catecholaminergic systems and the coordination of these systems with other homeostatic systems in health, stress, and disease. Findings this year include: (1) Position-emission tomographic (PET) scanning after systemic administration of 6-[18F]fluorodopamine ([18F]-6F-DA) provided a noninvasive, in vivo means to examine cardiac sympathetic innervation and function in humans. (2) Clinical microneuro- graphic and tracer norepinephrine (NE) kinetic methods were applied to diagnose neurocardiologic disorders, test the "epinephrine hypothesis" of sympathetic neurotransmission, and assess catechol~aminergic effects of glucocorticoids in humans. (3) In vivo microdialysis revealed juvenile spontaneously hypertensive rats have increased alpha2-adrenoceptor- mediated restraint of catecholamine biosynthesis and NE release in the posterolateral hypothalamus. (4) Patterning of neuroendocrine responses has supported a homeostat theory of stress.